Influence of diet on the metabolic turnover of stable isotope ratios and fatty acids in the omnivorous shrimp Palaemon peringueyi

Abstract

Determination of the tissue turnover rates of natural tracers such as stable isotope ratios and fatty acids in an organism is a prerequisite for elucidating trophic interactions in ecological studies. We conducted a 72-day diet-switch experiment to quantify temporal fluctuations in the carbon and nitrogen stable isotope values and fatty acid profiles in the muscle tissues of an omnivorous shrimp Palaemon peringueyi. As the food source was switched from fresh seagrass to live Artemia, nonlinear models were used to calculate tracer turnover rates and their proportional contributions to growth and metabolism. Carbon half-life was faster (0.8 days) in seagrass-fed shrimps compared to Artemia-fed shrimps (231 days), whereas nitrogen turnover (0.7 days) and fatty acid turnover (1.5–4 days) showed faster half-lives in Artemia-fed shrimps. As the shrimps showed limited growth, most of the turnover of the tracer components was attributed to metabolism (>50 %). Fatty acids generally revealed faster half-lives (0.8–23 days) relative to stable isotope ratio half-lives (0.7–231 days), suggesting unequal efficiency of each tracer to elucidate temporal variations in the consumer’s diet. Our results have significant implications for temporal studies that use tracers, especially when consumers have the potential to change diets. Variations in the metabolic turnover rates of stable isotope ratios and fatty acids in the muscle tissues of the shrimp were largely driven by the quality of the food provided and revealed physiological flexibility in an omnivorous consumer.